Simultaneous Use of Amiodarone Influences Warfarin Maintenance Dose but Is Not Associated with Adverse Events

Author(s)

Junior Lima Santos, Paulo Caleb ; Gadi Soares, Renata Alonso ; Cassaro Strunz, Celia Maria ; Grinberg, Max ; Ferreira, Joao Fernando M. . ; Machado Cesar, Luiz Antonio ; Scanavacca, Mauricio ; Krieger, Jose Eduardo ; Pereira, Alexandre Costa

• Document type: Journal article
• Source: JOURNAL OF MANAGED CARE & SPECIALTY PHARMACY; v. 20, n. 4, p. 6-pg., 2014-04-01.

Abstract

BACKGROUND: Drug interaction studies selecting patients in a real-life setting are scarce, and most studies to date are characterized by a small sample size. OBJECTIVE: To evaluate the effect of amiodarone on warfarin maintenance dose and adverse events in an anticoagulation cohort from a tertiary cardiovascular service. METHODS: This study recruited 866 patients, and oral anticoagulant therapy was monitored by the prothrombin time expressed as the international normalized ratio (INR). Genotyping of CYP2C9*2, CYP2C9*3, and VKORC1 3673 polymorphisms was performed. RESULTS: Of the 866 patients, 111 (12.8%) were taking amiodarone and warfarin simultaneously, and 514 (59.4%) reached the therapeutic target dose. The warfarin maintenance dose was significantly lower in patients simultaneously using amiodarone (23.8 +/- 11.3 mg/wk) compared with other patients (29.5 +/- 14.3 mg/wk; P < 0.001). Patients taking amiodarone had higher INR/current dose ratios (0.83 +/- 0.04 per mg) compared with patients not using amiodarone (0.71 +/- 0.02 per mg, P = 0.001). Adverse event frequency was not different between the groups (P = 0.40). No genotype effect was noted on the odds of bleeding associated with amiodarone use. CONCLUSIONS: Simultaneous use of amiodarone influences warfarin maintenance dose, but is not associated with adverse events. Copyright (C) 2014, Academy of Managed Care Pharmacy. All rights reserved (AU)

• FAPESP's process: 10/17881-1 - Pharmacogenetic analysis using warfarin drug and in the Brazilian general population
• Grantee: Renata Alonso Gadi Soares
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 10/17465-8 - Pharmacogenetic analysis using drugs of the cardiovascular system and in the Brazilian general population
• Grantee: Paulo Caleb Júnior de Lima Santos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral